U.S. patent number 7,215,326 [Application Number 10/674,423] was granted by the patent office on 2007-05-08 for physically realistic computer simulation of medical procedures.
This patent grant is currently assigned to Immersion Corporation. Invention is credited to Louis B. Rosenberg.
United States Patent |
7,215,326 |
Rosenberg |
May 8, 2007 |
**Please see images for:
( Certificate of Correction ) ** |
Physically realistic computer simulation of medical procedures
Abstract
An apparatus for interfacing the movement of a shaft with a
computer includes a support, a gimbal mechanism having two degrees
of freedom, and three electromechanical transducers. When a shaft
is engaged with the gimbal mechanism, it can move with three
degrees of freedom in a spherical coordinate space, where each
degree of freedom is sensed by one of the three transducers. A
fourth transducer can be used to sense rotation of the shaft around
an axis. The method includes the steps of defining an origin in
3-dimensional space, physically constraining a shaft in the
3-dimensional space such that a portion of the shaft always
intersects the origin and such that a portion of the shaft
extending beyond the origin defines a radius in a spherical
coordinate system, transducing a first electrical signal related to
a first angular coordinate of the radius with a first transducer,
transducing a second electrical signal related to a second angular
coordinate with a second transducer, transducing a third electrical
signal related to the length of the radius with a third transducer,
and coupling the transducers to a computer.
Inventors: |
Rosenberg; Louis B. (Mountain
View, CA) |
Assignee: |
Immersion Corporation (San
Jose, CA)
|
Family
ID: |
23050952 |
Appl.
No.: |
10/674,423 |
Filed: |
October 1, 2003 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20040066369 A1 |
Apr 8, 2004 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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09996487 |
Nov 27, 2001 |
6654000 |
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09276012 |
Mar 25, 1999 |
6323837 |
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08833502 |
Apr 7, 1997 |
6037927 |
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08275120 |
Jul 14, 1994 |
5623582 |
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Current U.S.
Class: |
345/158;
715/701 |
Current CPC
Class: |
B25J
9/1689 (20130101); G05B 19/409 (20130101); G16H
50/50 (20180101); A61B 34/76 (20160201); G05B
2219/35338 (20130101); G05B 2219/35441 (20130101); G05B
2219/40137 (20130101); G05B 2219/45118 (20130101); A61B
34/10 (20160201); G05B 2219/40119 (20130101) |
Current International
Class: |
G09G
5/00 (20060101) |
Field of
Search: |
;345/7,8,156-158,161,166,184,700-702 ;434/262,267 |
References Cited
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JP |
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Dec 1996 |
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WO |
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|
Primary Examiner: Liang; Regina
Attorney, Agent or Firm: Thelen Reid Brown Raysman &
Steiner LLP Ritchie; David B.
Parent Case Text
This application is a continuation of U.S. application Ser. No.
09/996,487, filed Nov. 27, 2001, now U.S. Pat. No. 6,654,000, which
is a continuation of U.S. application Ser. No. 09/276,012, filed
Mar. 25, 1999, now U.S. Pat. No. 6,323,837, which is a continuation
of application Ser. No. 08/833,502, filed Apr. 7, 1997 now U.S.
Pat. No. 6,037,927, which is a continuation of application Ser. No.
08/275,120, filed Jul. 14, 1994, now U.S. Pat. No. 5,623,582, all
of which are incorporated herein by reference in their entireties.
Claims
What is claimed is:
1. A method for computer simulation, comprising: generating a
virtual reality simulation on a host computer having a display;
manipulating a medical instrument coupled to an interface including
a mechanism, the medical instrument slidably moveable through an
aperture of the mechanism along a linear degree of freedom; sensing
movement of the medical instrument in at least two rotary degrees
of freedom and the linear degree of freedom; transmitting position
information of the medical instrument at the interface based on the
sensed movement to the host computer; updating the displayed
virtual reality simulation in response to the updated position
information; selectively transmitting a force command from the host
computer to the interface based on the updated position
information; and generating a force feedback sensation on the
medical instrument in response to the force command.
2. The method of claim 1, further comprising executing a local
software routine at the interface.
3. The method of claim 1, further comprising detecting rotary
motion of the portion of the medical instrument about a first axis
and detecting rotary motion of the portion of the medical
instrument about a second axis, wherein the first and second axes
are substantially perpendicular to one another.
4. The method of claim 1, wherein generating the virtual reality
simulation further comprising simulating at least a portion of a
body of a patient.
5. The method of claim 1, wherein generating the force feedback
sensation further comprises generating a resistance force to act
against the movement of the medical instrument.
6. The method of claim 1, wherein generating the force feedback
sensation further comprises generating a twisting force on a shaft
of the medical instrument.
7. The method of claim 1, wherein generating the force feedback
sensation further comprises generating a force along the linear
degree of freedom.
8. The method of claim 1, wherein generating the force feedback
sensation further comprises generating a force along at least one
of the rotary degrees of freedom.
9. A medical simulation system comprising: an interface adapted to
receive a medical instrument, the interface including a mechanism
having an aperture to slidably receive at least a portion of the
medical instrument along a linear degree of freedom, the interface
configured to track movement of the medical instrument along the
linear degree of freedom and at least two rotary degrees of
freedom; a host computer configured to generate a virtual reality
representation on a display, the host computer coupled to the
interface and configured to receive position information associated
with the tracked movement of the medical instrument, wherein the
host computer is configured to update the displayed virtual reality
simulation based on the received position information and
selectively output a force command; and wherein the interface
includes an actuator configured to provide a force feedback
sensation to the medical instrument in response to receiving the
force command.
10. The simulation system of claim 9, wherein the at least two
rotary degrees of freedom further comprises a first degree of
motion along a first axis and a second degree of freedom along a
second axis, wherein the first and second axes are substantially
perpendicular to one another.
11. The simulation system of claim 9, wherein the interface further
comprises a first sensor configured to detect rotary motion of the
medical instrument about a first axis and a second sensor is
configured to detect rotary motion of the medical instrument about
a second axis substantially perpendicular to the first axis.
12. The simulation system of claim 9, wherein the interface further
comprises a linear sensor configured to detect linear motion of the
medical instrument along an axis coaxial with the aperture.
13. The simulation system of claim 9, wherein the virtual reality
representation is that of a patient's body.
14. The simulation system of claim 9, wherein the virtual reality
representation includes a graphical representation of the medical
instrument.
15. The simulation system of claim 9, wherein the force feedback
sensation opposes a directed force by the user on the medical
instrument.
16. The simulation system of claim 9, wherein the medical
instrument represents a laparoscopic instrument and is formed in a
shape of a physical laparoscopic instrument handle.
17. The simulation system of claim 9, wherein the medical
instrument is a catheter and a portion of the medical instrument is
formed in a shape of a catheter wire.
18. The simulation system of claim 9, wherein the force feedback
includes a twisting force on a shaft of the medical instrument.
19. The simulation system of claim 9, wherein the force feedback
includes a linear force on a shaft of the medical instrument.
20. The simulation system of claim 9, the actuator applies force to
the medical instrument through a frictional engagement of a drive
wheel.
21. An apparatus for computer simulation comprising: means for
generating a virtual reality simulation on a host computer having a
display; means for engaging a medical instrument, wherein the
medical instrument is slidably moveable through an aperture along a
linear degree of freedom in said means for engaging; means for
sensing movement of the medical instrument in at least two rotary
degrees of freedom and the linear degree of freedom; means for
transmitting position information of the medical instrument on the
sensed movement; means for updating the displayed virtual reality
simulation in response to the updated position information; means
for selectively transmitting a force command from said means for
generating to said means for engaging based on the updated position
information; and means for generating a force feedback sensation on
the medical instrument in response to the force command.
22. The apparatus of claim 21, further comprising means for
executing a local software routine in response to receiving the
force command.
23. The apparatus of claim 21, wherein said means for engaging is
configured to allow at least a portion of the medical instrument to
operate with at least two degrees of freedom supported by a gimbal
mechanism.
24. The apparatus of claim 21, further comprising first means for
sensing rotary motion of the medical instrument about a first
axis.
25. The apparatus of claim 24, further comprising secpmd means for
detecting rotary motion of the medical instrument about a second
axis.
26. The apparatus of claim 21, wherein the virtual reality
simulation includes at least a portion of a body of a patient.
27. The apparatus of claim 21, wherein the virtual reality
simulation includes a graphical representation of the medical
instrument.
28. The apparatus of claim 21, wherein said means for generating
generates a resistance force to act against the movement of the
medical instrument.
29. The apparatus of claim 21, wherein said means for generating
generates a rotary torque on a shaft of the medical instrument.
Description
BACKGROUND OF THE INVENTION
This invention relates generally to human/computer interface
devices, and more particularly to computer input devices such as
mice, trackballs, etc.
Virtual reality computer systems provide users with the illusion
that they are part of a "virtual" environment. A virtual reality
system will typically include a personal computer or workstation,
specialized virtual reality software, and virtual reality I/O
devices such as head mounted displays, pointer gloves, 3D pointers,
etc.
For example, a virtual reality computer system can allow a
doctor-trainee or other human operator or user to "manipulate" a
scalpel or probe within a computer-simulated "body", and thereby
perform medical procedures on a virtual patient. In this instance,
the I/O device is typically a 3D pointer, stylus, or the like. As
the "scalpel" or "probe" moves within the body image displayed on
the screen of the computer system, results of such movement are
updated and displayed so that the operator can gain the experience
of such a procedure without practicing on an actual human being or
a cadaver.
For virtual reality systems to provide a realistic (and therefore
effective) experience for the user, sensory feedback and manual
interaction should be as natural as possible. As virtual reality
systems become more powerful and as the number of potential
applications increases, there is a growing need for specific
human/computer interface devices which allow users to interface
with computer simulations with tools that realistically emulate the
activities being represented within the virtual simulation. Such
procedures as laparoscopic surgery, catheter insertion, and
epidural analgesia should be realistically simulated with suitable
human/computer interface devices if the doctor is to be properly
trained.
While the state of the art in virtual simulation and medical
imaging provides a rich and realistic visual feedback, there is a
great need for new human/computer interface tools which allow users
to perform natural manual interactions with the computer
simulation. For medical simulation, there is a strong need to
provide doctors with a realistic mechanism for performing the
manual activities associated with medical procedures while allowing
a computer to accurately keep track of their actions.
There are number of devices that are commercially available for
interfacing a human with a computer for virtual reality
simulations. There are, for example, such 2-dimensional input
devices such as mice, trackballs, and digitizing tablets. However,
2-dimensional input devices tend to be awkward and inadequate to
the task of interfacing with 3-dimensional virtual reality
simulations. In contrast, a 3-dimensional human/computer interface
tool sold under the trademark Immersion PROBE.TM. is marketed by
Immersion Human Interface Corporation of Palo Alto, Calif., and
allows manual control in 3-dimensional virtual reality computer
environments. A pen-like stylus allows for dexterous 3-dimensional
manipulation, and the position and orientation of the stylus is
communicated to a host computer. The Immersion PROBE has six
degrees of freedom which convey spatial coordinates (x, y, z) and
orientation (role, pitch, yaw) of the stylus to the host
computer.
While the Immersion PROBE is an excellent 3-dimensional interface
tool, it may be inappropriate for certain virtual reality
simulation applications. For example, in some of the aforementioned
medical simulations three or four degrees of freedom of a
3-dimensional human/computer interface tool is sufficient and,
often, more desirable than five or six degrees of freedom because
it more accurately mimics the real-life constraints of the actual
medical procedure. Therefore, a less complex, more compact, lighter
weight, lower inertia and less expensive alternative to six degree
of freedom human/computer interface tool is desirable for certain
applications.
SUMMARY OF THE INVENTION
The present invention provides a 3-dimensional human/computer
interface tool which is particularly well adapted to virtual
reality simulation systems that require fewer degrees of freedom,
e.g. two, three, or four degrees of freedom. The present invention
therefore tends to be less complex, more compact, lighter weight,
less expensive, more reliable and have less inertia than
3-dimensional human/computer interface tools of the prior art
having more degrees of freedom.
The present invention is directed to a method and apparatus for
providing an interface between a human and a computer. The human
end of the interface is preferably a substantially cylindrical
object such as a shaft of a surgeon's tool, a catheter, a wire,
etc. Alternatively, it can comprise a pool cue, a screw driver
shaft, or any other elongated object that is manipulated in
3-dimensional space by a human operator. In certain embodiments of
the present invention, the computer develops signals to provide
force feedback to the object. For example, a twisting or resisting
force can be imparted on the object to provide haptic or force
feedback of a medical procedure being performed in a virtual
reality simulation.
An apparatus for interfacing with a electrical system includes a
support, a gimbal mechanism coupled to the support, and preferably
three electromechanical transducers, although certain embodiments
(e.g. for use with catheters) may require only two
electromechanical transducers. The gimbal mechanism has a base
portion which is rotatably coupled to the support to provide a
first degree of freedom, and an object receiving portion rotatably
coupled to the base portion to provide a second degree of freedom.
A first electromechanical transducer is coupled between the support
and the base portion, a second electromechanical transducer is
coupled between the base portion and the object receiving portion,
and a third electromechanical transducer is coupled between the
object receiving portion and an intermediate portion of an
elongated object that is at least partially disposed within the
object receiving portion. The third electromechanical transducer is
associated with a third degree of freedom. Therefore, each of the
three transducers are associated with a degree of freedom of
movement of the object when it is engaged with the object receiving
portion of the gimbal mechanism.
More specifically, an apparatus for interfacing an operator
manipulable shaft with a computer includes a support, a gimbal
mechanism, and four sensors. The gimbal mechanism preferably
includes a U shaped base portion having a base and a pair of
substantially parallel legs extending therefrom, where the base of
the U shaped base portion is rotatably coupled to the support, and
a shaft receiving portion pivotally coupled between the legs of the
base portion. The shaft receiving portion includes a translation
interface and a rotation interface that engage the shaft when it is
engaged with an aperture of the shaft receiving portion. The base
portion rotates around a first axis and the shaft receiving portion
rotates around a second axis substantially perpendicular to the
first axis, such that an axis of the shaft defines a radius in a
spherical coordinate system having an origin at an intersection of
the first axis and the second axis. A first sensor is coupled
between the support and the U shaped base portion to provide a
first output signal, a second sensor is coupled between the U
shaped base portion and the shaft receiving portion to produce a
second output signal, a third sensor is coupled to the translation
interface to produce a third output signal, and a fourth sensor is
coupled between the rotation interface and the object to produce a
fourth output signal. The output signals are preferably coupled to
an input of a computer by an electronic interface.
In an alternative embodiment of the present invention a first
actuator is coupled between the support and the U shaped base
portion to produce a movement therebetween in response to a first
input electrical signal, a second actuator is coupled between the U
shaped base portion and the shaft receiving portion to produce a
movement therebetween in response to a second input electrical
signal, a third actuator is coupled to the translation interface to
produce a mechanical movement of the elongated cylindrical object
relative to the shaft receiving portion in response to a third
input electrical signal, and a fourth actuator is coupled to the
rotation interface to produce a mechanical movement of the
elongated cylindrical object relative to the shaft receiving
portion in response to a fourth input electrical signal.
A method for providing a human/computer interface includes the
steps of: (a) defining an origin in a 3-dimensional space; (b)
physically constraining a shaft that can be grasped by an operator
such that a portion of the object always intersects the origin and
such that the portion of the object extending past the origin
defines a radius in a spherical coordinate system; (c) transducing
a first electrical signal related to a first angular coordinate of
the radius in the spherical coordinate system with a first
transducer; (d) transducing a second electrical signal related to a
second angular coordinate of the radius in the spherical coordinate
system with a second transducer; (e) transducing a third electrical
signal related to the length of the radius with a third transducer;
and (f) electrically coupling the transducers to a computer system
to provide a human/computer interface. The method can further
include the step of transducing a fourth electrical signal related
to a rotation of the shaft around an axis with a fourth transducer.
The transducers are either sensors, actuators, or bi-directional
transducers which can serve as either input or sensors.
It will therefore be appreciated that a human/computer interface of
the present invention includes a support, a gimbal mechanism
coupled to the support, and an elongated shaft engaged with the
gimbal mechanism and having a grip area that can be grasped by a
hand of an operator. The gimbal mechanism has a base portion
rotatably coupled to the support, and a shaft receiving portion
rotatably coupled to the base. A first sensor is coupled between
the support and the base portion, a second sensor is coupled
between the base portion and the shaft receiving portion, and a
third sensor is coupled between the shaft receiving portion and an
intermediate portion of the shaft. The three sensors are coupled to
an input of a computer to provide the human/computer interface.
Preferably, the interface further includes a fourth sensor coupled
between the shaft receiving portion and an intermediate portion of
the shaft, where the third sensor is a translation sensor and the
fourth sensor is a rotation sensor.
The advantage of the present invention is that a 3-dimensional
human/computer interface tool is provided which has the three or
four degrees of freedom available that are desirable for many
virtual reality simulation applications. The mechanism of the
present invention is relatively straightforward allowing for low
cost production and high reliability. Furthermore, since the
human/computer interface tool of the present invention is
constrained from movement along at certain degrees of freedom, it
can more accurately simulate the use of tools and other elongated
mechanical objects which are similarly constrained. Importantly,
the present interface is of low inertia since the primary mass of
the interface is located at the pivot point. This, along with the
light weight of the interface, makes the interface less fatiguing
to use.
In another embodiment of the present invention a human/computer
interface tool is provided which is provided with only two degrees
of freedom. This is particularly advantageous when the shaft is
flexible, such as with very thin shafts, wires, catheters, and the
like. With, for example, catheters, it is only necessary to provide
two degrees of freedom (i.e. in-and-out, and rotation) and,
therefore, sensors and/or actuators for the other degrees of
freedom do not need to be provided.
These and other advantages of the present invention will become
apparent to those skilled in the art upon a reading of the
following descriptions of the invention and a study of the several
figures of the drawing.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a virtual reality system which
employs an apparatus of the present invention to interface a
laparoscopic tool handle with a computer system;
FIG. 2 is a perspective view of an apparatus for mechanically
interfacing an elongated mechanical object with an electrical
system in accordance with the present invention;
FIG. 2a is a perspective view of an alternative translation
interface used for wires, catheters, and the like;
FIG. 3 is front elevation view of the apparatus of FIG. 2
illustrating a laparoscopic tool engaged with an object receiving
portion of the present invention;
FIG. 4 is a side elevation similarly showing a laparoscopic tool
engaged with the object receiving portion of the present
invention;
FIG. 5 is a top plan view also illustrating the engagement of a
laparoscopic tool with the object receiving portion of the present
invention;
FIG. 6 is a pictorial view illustrating the four degrees of freedom
enjoyed with the mechanism of the present invention;
FIG. 7 illustrates a first embodiment of an input sensor;
FIG. 8 illustrates a modified laparoscopic tool handle for the use
of the present invention;
FIG. 8a is a cross-section taken along line 8a--8a of FIG. 8;
FIG. 9 is a perspective view of a sensor in accordance with the
present invention;
FIG. 9a is a sectional view taken along line 9a--9a of FIG. 9;
FIG. 9b is a perspective view of an alternative sensing wheel used
for wires, catheters, and the like;
FIG. 10 is a perspective view of and alternative sensor mechanism
of the present invention;
FIG. 10a is a cross sectional view taken along line 10a--10a of
FIG. 10;
FIG. 11 is a perspective view of another alternative sensor of the
present invention; and
FIG. 11a is a sectional view-taken along line 11a--11a of FIG.
11.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In FIG. 1, a virtual reality system 10 includes a human/computer
interface apparatus 12, a electronic interface 14, and a computer
16. The illustrated virtual reality system 10 is directed to a
virtual reality simulation of a laparoscopic surgery procedure. The
software of the simulation is not a part of this invention and thus
will not be discussed in any detail. However, such software is
commercially available as, for example, Teleos.TM. from High
Techsplanations of Rockville, Md. Suitable software drivers which
interface such simulation software with computer input/output (I/O)
devices are available from Immersion Human Interface Corporation of
Palo Alto, Calif.
A laparoscopic tool 18 used in conjunction with the present
invention is manipulated by an operator and virtual reality images
are displayed on a screen 20 of the digital processing system in
response to such manipulations. Preferably, the digital processing
system is a personal computer or workstation, such as an IBM-PC AT
or Macintosh personal computer, or a SUN or Silicon Graphics
workstation. Most commonly, the digital processing system is a
personal computer which operates under the MS-DOS operating system
in conformance with an IBM PC AT standard.
The human/interface apparatus 12 as illustrated herein is used to
simulate a laparoscopic medical procedure. In addition to a
standard laparoscopic tool 18, the human/interface apparatus 12
includes a barrier 22 and a standard laparoscopic trocar 24. The
barrier 22 is used to represent portion of the skin covering the
body of a patient. Trocar 24 is inserted into the body of the
patient to provide an entry and removal point from the body of the
patient for the laparoscopic tool 18, and to allow the manipulation
of the laparoscopic tool 18 within the body of the patient while
minimizing tissue damage. Laparoscopic tools 18 and trocars 24 are
commercially available from sources such as U.S. Surgical of
Connecticut. Preferably, the laparoscopic tool 18 is modified such
that the end of the tool (such as any cutting edges) are removed,
leaving only the handle and the shaft. The end of the laparoscopic
tool 18 is not required for the virtual reality simulation, and is
removed to prevent any potential damage to persons or property. A
gimbal apparatus 25 is shown within the "body" of the patient in
phantom lines.
The laparoscopic tool 18 includes a handle or "grip" portion 26 and
a shaft portion 28. The shaft portion is an elongated mechanical
object and, in particular, is an elongated cylindrical object. The
present invention is concerned with tracking the movement of the
shaft portion 28 in three-dimensional space, where the movement has
been constrained such that the shaft portion 28 has only three or
four free degrees of motion. This is a good simulation of the real
use of a laparoscopic tool 18 in that once it is inserted into a
trocar 24 and through the gimbal apparatus 25, it is limited to
about four degrees of freedom. More particularly, the shaft 28 is
constrained at some point of along its length such that it can move
with four degrees of freedom within the patient's body.
While the present invention will be discussed with reference to the
shaft portion 28 of laparoscopic tool 18, it will be appreciated
that a great number of other types of objects can be used with the
method and apparatus of the present invention. In fact, the present
invention can be used with any elongated mechanical object where is
desirable to provide a human/computer interface with three or four
degrees of freedom. Such objects may include catheters, hypodermic
needles, wires, fiber optic bundles, screw drivers, pool cues, etc.
Furthermore, although the described preferred embodiment of the
present invention contemplates the use of a elongated cylindrical
mechanical object, other embodiments of the present invention
provide a similar human/computer interface for an elongated
mechanical objects which are not cylindrical in shape.
The electronic interface 14 is a part of the human/computer
interface apparatus 12 and coupled the apparatus 12 to the computer
16. An electronic interface 14 that is particularly well adopted
for the present is described in U.S. patent application Ser. No.
08/092,974, filed Jul. 16, 1993, now U.S. Pat. No. 5,576,727
assigned to the assignee of the present invention and incorporated
herein by reference in its entirety. The electronic interface
described therein was designed for the Immersion PROBE.TM. 3-D
mechanical mouse and has six channels corresponding to the six
degrees of freedom of the Immersion PROBE. However, in the context
of the present invention, the electronic interface 14 requires the
use of only four of the six channels, since the present invention
is preferably constrained to no more than four degrees of
freedom.
The electronic interface 14 is coupled to a gimbal apparatus 25 of
the apparatus 12 by a cable 30 and is coupled to the computer 16 by
a cable 32. In some embodiments of the present invention, interface
14 serves solely as an input device for the computer 16. In other
embodiments of the present invention, interface 14 serves solely as
an output device for the computer 16. In yet other embodiments of
the present invention, the interface 14 serves as an input/output
(I/O) device for the computer 16.
In an alternative embodiment of the present invention, interface 14
has a local microprocessor 33 preferably coupled with any
transducers present in the interface 14 and with a transceiver 35.
In such an embodiment, the computer 16 is coupled to the
transceiver 35 and, typically, not coupled directly with any
transducers present in the interface 14. As will be appreciated,
the transceiver 35 may be any suitable transceiver capable of
bi-directional communication through serial or parallel
communication strategies. The local microprocessor 33 will be
programmed to execute computer instructions locally such that a
computing burden is removed from the computer 16. For example,
positional information generated by the transducers may be
processed locally by the local microprocessor 33, which in turn can
send absolute position and velocity information to the computer 16.
Still further, the local microprocessor 33 is capable of receiving
incoming force commands from the computer 16, decoding such
commands, and controlling the interface 14 accordingly. For more
details, see U.S. Pat. No. 5,576,727 of Rosenberg et al.
In the perspective view of FIG. 2, the gimbal apparatus 25 of the
present invention is illustrated in some detail. The gimbal
apparatus 25 includes a support 34 and a gimbal mechanism 36
rotatably coupled to the support. The gimbal mechanism 36
preferably includes a U shaped base portion 38 including a base 40
and a pair of substantially parallel legs 42a and 42b extending
upwardly therefrom. As used herein, "substantially parallel" will
mean that two objects or axis are exactly or almost parallel, i.e.
are at least within five or ten degrees of parallel, and are
preferably within less than one degree of parallel. Similarly, the
term "substantially perpendicular" will mean that two objects or
axis are exactly or almost perpendicular, i.e. at least within five
degrees or ten degrees of perpendicular, or more preferably within
less than one degree of perpendicular.
The gimbal mechanism 36 also includes an elongated object (shaft)
receiving portion 44 provided with an aperture 46 which extends
entirely through the object receiving portion. The aperture 46
defines an object axis A.sub.0 for an elongated cylindrical object,
such that the shaft portion 28 of the laparoscopic tool 18 of FIG.
1. The object receiving portion 44 is at least partially disposed
between the legs 42a and 42b of the U shaped base portion, and is
pivotally coupled thereto such as by a pair of pivots, one of which
is shown as pivot 48a in leg 42a. Another pivot 48b (not shown) is
provided in leg 42b.
The object receiving portion 44 also includes a translation
interface 50 and a rotation interface 52. The object receiving
portion 44 includes a bearing section 54, a translation sensor
section 56, and a rotation sensor section 58. The bearing section
54 includes a mass of material provided with a cylindrical bore 60
forming a portion of the aperture 46. The translation sensor
section 56 includes a pair of opposing wall surfaces 62a and 62b,
each of which is provided with a cylindrical bore receptive to the
cylindrical object and forming a part of the aperture 46 which
extends through the object receiving portion. The translation
sensor section 56 includes a pair of opposing wall surfaces 64a and
64b of a wall 63 and which are provided with cylindrical bores
receptive to the cylindrical object and therefore also forming a
part of the aperture 46. In consequence, when an elongated
cylindrical object is inserted into the object receiving portion 44
along axis A.sub.0 it engages the bore 60 of the bearing section
54, and extends through bores provided in the surfaces 62a, 62b,
64a, and 64b to extend completely through the object receiving
portion 44 along the aperture 46. In another embodiment of the
present invention, wall 63 (and therefore wall surfaces 64a and
64b) is eliminated as being superfluous.
Referring briefly to FIG. 2a, an alternative construction for the
translation interface 50 of FIG. 2 is shown at 50'. This
alternative translation interface 50' is well adapted for very thin
shafts, wires, catheters, and the like. The problem encountered
with the translation interface 50 is that, for example, wires and
catheters are flexible and therefore do not engage well with a
single friction wheel. Therefore, the translation interface 50'
includes a drive wheel 65a that is coupled to a sensor and/or
actuator, and an idler wheel 65b. The wire or catheter 67 is
pinched between the drive wheel 65a and the idler wheel 65b so that
there is good frictional engagement between the catheter 67 and the
drive wheel 65a.
The object receiving portion 44 is preferably a unitary mass of
material made from aluminum or some other lightweight material such
as a plastic. The object receiving portion 44 is preferably cast,
molded, and/or machined as a monoblock member having the
aforementioned bearing section, translation sensory section, and
rotation sensory section. The materials and construction of U
shaped base portion 38 preferably match the materials and
construction techniques used for the production of object receiving
portion 44.
The gimbal apparatus 25 illustrated in FIG. 2 constrains an object
that is engaged with the object receiving portion 44 to four
degrees of freedom. This is accomplished by allowing the U shaped
base portion 38 to rotate around an axis A.sub.1 relative to the
support 34, by allowing the object receiving portion 44 to rotate
around an axis A.sub.2 relative to the U shaped base portion 38, by
allowing the object to translate as illustrated by the arrow t
along axis A.sub.0 of aperture 46, and by allowing the object to
rotate as indicated by arrow r around the axis A.sub.0 of aperture
46.
Four electromechanical transducers are used in association with
these four degrees of freedom. More particularly, a first degree of
freedom electromechanical transducer 66 is arranged to transduce
motion and/or force between the U shaped base portion 38 and the
support 34, a second degree of freedom electromechanical transducer
68 is arranged to transduce motion and/or force between the U
shaped base portion 38 and the object receiving portion 44, a third
degree of freedom electromechanical transducer 70 is arranged to
transduce motion and/or force between the object receiving portion
44 and an object engaged with the object receiving portion 44, and
a fourth degree of freedom transducer 72 is arranged to transduce
motion and/or force between the object receiving portion 44 and an
object engaged with the object receiving portion 44.
By "associated with", "related to", or the like, it is meant that
the electromechanical transducer is influenced by or influences one
of the four degrees of freedom. The electromechanical transducers
can be input transducers, in which case they sense motion along a
respective degree of freedom and produce an electrical signal
corresponding thereto for input into computer 16. Alternatively,
the electromechanical transducers can be output transducers which
receive electrical signals from computer 16 that cause the
transducers to impart a force on the object in accordance with
their respective degrees of freedom. The electromechanical
transducers can also be hybrid or bi-directional transducers which
operate both as sensors and as actuator devices.
A variety of transducers, readily available in the commercial
market are suitable for use in the present invention. For example,
if the transducers are input transducers ("sensors"), such sensors
can include encoded wheel transducers, potentiometers, etc. Output
transducers ("actuators") include stepper motors, servo motors,
magnetic particle brakes, friction brakes, pneumatic actuators,
etc. Hybrid or bi-directional transducers often pair input and
output transducers together, but may also include a purely
bi-directional transducer such as a permanent magnet electric
motor/generator.
It should be noted that the present invention can utilize both
absolute and relative sensors. An absolute sensor is one which the
angle of the sensor is known in absolute terms, such as with an
analog potentiometer. Relative sensors only provide relative angle
information, and thus require some form of calibration step which
provide a reference position for the relative angle information.
The sensors described herein are primarily relative sensors. In
consequence, there is an implied calibration step after system
power-up wherein the shaft is placed in a known position within the
gimbal mechanism and a calibration signal is provided to the system
to provide the reference position mentioned above. All angles
provided by the sensors are thereafter relative to that reference
position. Such calibration methods are well known to those skilled
in the art and, therefore, will not be discussed in any great
detail herein.
A preferred input transducer for use of the present invention is an
optical encoder model SI marketed by U.S. Digital of Vancouver,
Wash. This transducer is an encoded wheel type input transducer. A
preferred output transducer for use of the present invention is a
d.c. motor model 2434.970-50 produced by Maxon of Fall River, Mass.
This type of transducer is a servo motor type output
transducer.
There a number of ways of attaching the transducers to the various
members of the gimbal apparatus 25. In this preferred embodiment, a
housing of transducer 66 is attached to the U shaped base portion
38, and a shaft of the transducer extends through an oversize bore
(not shown) in base 40 to engage a press-fit bore (also not shown)
in support 34. Therefore, rotation of the U shaped base portion 38
around axis A.sub.1 will cause a rotation of a shaft of transducer
66. A housing of transducer 68 is attached to leg 42a of the U
shaped base portion 38 such that its shaft forms pivot 48a.
Therefore rotation of the object receiving portion 44 around axis
A.sub.2 will cause a rotation of the shaft of a second transducer
68. The transducer 70 is attached to object receiving portion 44
and extends through a bore (not shown) in a wall 74 of the
translation sensor section 56. The shaft 76 provides an axis about
which the translation interface 50 can rotate. The fourth
transducer 74 is attached to a wall 78 of rotation sensor section
58 and extends through a bore 80 in that wall 78. The shaft 82 of
the transducer 72 engages a circumferential surface of rotation
interface 52 and rotates therewith.
Axes A.sub.1 and A.sub.2 are substantially mutually perpendicular
and intersect at an origin point O within object receiving portion
44. Axis A.sub.0 also intersects this origin O. Shaft 76 rotates
around an axis A.sub.3 which is substantially perpendicular to the
axis A.sub.0. Shaft 58 of transducer 72 rotates around an axis
A.sub.4 which is substantially parallel to the axis A.sub.0.
In FIG. 3, a front view of the gimbal apparatus 25 is used to
illustrate one of the degrees of motion of the laparoscopic tool
18. The illustrated degree of freedom is the fourth degree of
freedom, i.e. rotation around axis A.sub.0 as illustrated by the
arrow r in FIG. 2. This degree of freedom is detected by transducer
72. In this fourth degree of motion, the handle portion 26 of the
laparoscopic tool 18 can rotate in a clockwise direction as
indicated at 26' and in a counter clockwise direction as indicated
at 26''. Of course, the handle 26 can rotate a full 360.degree.
although this would require the release and re-grasping of the
handle 26.
In FIG. 4, a second degree of freedom is illustrated. With this
degree of freedom, the laparoscopic tool 18 can pivot upwardly as
illustrated at 18' or downwardly (not shown). This rotation around
A.sub.2 is detected by transducer 68. It should be noted in the
present embodiment, the laparoscopic tool 18 cannot rotate
360.degree. around the axis A.sub.2 because it is physically
constrained by the support 34, portions of the gimbal mechanism 36,
etc. However, in the present embodiment, the laparoscopic tool can
achieve approximately 170 degrees of rotation around axis
A.sub.2.
FIG. 5 is top view of the gimbal apparatus 25 and illustrates the
first and third degrees of freedom. The first degree of freedom is
detected by transducer 66 as the laparoscopic tool 18 is pivoted or
rotated around axis A.sub.1 as illustrated at 18a and 18b. The
third degree of freedom is detected by transducer 70 as the shaft
portion 28 of laparoscopic tool 18 is moved back and fourth as
illustrated by the arrow "t." This causes a rotation of translation
interface 50 and the shaft 76 of the third transducer 70.
The four degrees of freedom are illustrated graphically in FIG. 6.
The cylinder 66' represents the first transducer 66 and allows a
first degree of freedom labeled "1st" around axis A.sub.1. Cylinder
68' represents the sensor 68 and allows a second degree of freedom
labeled "2nd" around axis A.sub.2. Telescoping members 70a' and
70b' represent the third sensor 70 can sense movement along a third
degree of freedom labeled "3rd" along axis A.sub.0. Finally, a
cylinder 72' attached to member 70b' represents the fourth
transducer 72 and senses a fourth degree of freedom labeled "4th"
around axis A.sub.0. A member 84 is provided to indicate position
and rotational direction relative to axis A.sub.0.
In FIG. 7, a preferred input transducer (sensor) of the present
invention is disclosed. Again, an input transducer of this type can
be purchased as sensor model SI from U.S. Digital of Vancouver,
Wash. The input transducer 86 includes a bearing block 88 having a
bearing 89, a rotary shaft 90 supported by the bearing 89, and a
sensing wheel 92 supported for rotation by shaft 90. The sensing
wheel is preferably made from a clear, plastic material and is
provided with a number of dark radial bands 94 near its
circumference, such as by printing or silk screening. A first
photodetector pair 96a including a light source 98a and a detector
100a are positioned on opposing sides of the sensing wheel 92 in
alignment with the bands 94. Similarly, a second photodetector pair
96b including a light source 98b and a detector 100b are positioned
on opposing sides of the sensing wheel 92 in alignment with the
bands 94. As the sensing wheel 92 rotates as illustrated at 102
around an axis A, the bands 94 alternatively allow light emanating
from light sources 98a and 98b to impinge or not impinge upon the
detectors 100a and 100b, respectively. The electronic interface 14,
coupled to the photodetector pairs 96a and 96b by cable 30, counts
the bands 94 as they pass the photodetector pairs 96a and 96b to
provide a signal on cable 32 to the computer 16 indicating the
rotational position of the shaft 90 around axis A. The two pairs
96a and 96b are provided to determine the direction of rotation, as
is well known to those skilled in the art of sensor design.
FIGS. 8 and 8a illustrate a modified laparoscopic tool 104. More
particularly, a sensor 106 has been added to determine when the
handle 108 has been squeezed, and the shaft 110 has been grooved or
slotted for a purpose to be discussed subsequently. The sensor 106
can be coupled to the computer 16 through electronic interface 14
to provide additional input to the virtual reality system.
With reference to FIG. 8a, the shaft 110 is preferably hollow,
having an axial bore 112 which aligns with axis A.sub.0, and is
provided with an elongated groove 114 which is parallel to an axis
A.sub.Lof the shaft 110. This elongated groove 114 can be produced
by any process including extruding the shaft 110 in the appropriate
shape, or cutting the groove 114 with a machine tool, etc.
FIGS. 9 and 9a illustrate an alternate embodiment for transducer 72
which utilizes the shaft 110 and a detector mechanism similar to
the one illustrated in FIG. 7. More particularly, the transducer
72' includes a sleeve 114 which is slidingly engaged with shaft
110. As seen in the cross sectional view of FIG. 9a, the sleeve 115
is a substantially cylindrical object having a central bore 116
which engages the circumference 118 of the shaft 110. The sleeve
115 has a key 120 which engages the groove 114 of the shaft 110.
Therefore, while the sleeve can slide back and forth along the axis
A.sub.Las indicated at 122, but the sleeve 115 rotates with the
shaft 110 as indicated at 124 due to the engagement of the key 120
with the groove 114. A sensing wheel 92' is affixed to a
circumferential portion of sleeve 115 so that it rotates coaxially
with the sleeve 115. A photodetector pair 96' senses the motion of
bands 94 ' and produces an electrical signal on cable 30. The
advantage of the embodiment shown in FIGS. 9 and 9a is that
rotation of the shaft around axis A.sub.Lis detected without the
possibility of slippage. Another advantage of this embodiment is
that it is more compact in design.
In FIG. 9b an alternate embodiment for a rotation interface 52' is
shown. This alternate embodiment is well adapted for flexible
shafts, wires, catheters and the like, such as the aforementioned
catheter 67. The rotation interface 52' includes a transducer
72'''' that is provided with a resilient grommet 73 having a hole
that engages a circumferential portion of the catheter 67. The
grommet 73 is preferably a rubber or plastic grommet that causes
the catheter 67 to rotate coaxially as the catheter spins or
rotates. Preferably, the mass of the transducer 72'''' is kept very
small so that it only takes a small amount of friction to ensure
coaxial rotation of the catheter and transducer without slippage.
Because the level of friction is so small, it does not
substantially impede translational motion (i.e. in-out motion) of
the catheter.
FIGS. 10 and 10a illustrate another embodiment 72'' for the
transducer 72 of FIG. 2. This embodiment has a number of points of
similarity with the embodiment discussed with reference to FIGS. 9
and 9a, and it will be appreciated that elements with like
reference numerals operate in a similar fashion. However, the
embodiment of FIGS. 10 and 10a include a sheave 126 affixed to the
circumference of sleeve 115 in the place of the sensing wheel 92'
of FIG. 9 and FIG. 9a. A position sensor 128 has a shaft 130 which
is coupled to the sheave 126 by a belt 132. The belt 132 can be any
continuous loop structure including a resilient, rubber-type belt,
a drive-chain type belt, etc. The shaft 130 of position sensor 128
therefore rotates with the sheave 126. The advantage of using a
belt 132 or the like is that a substantial amount of force may be
applied to the belt to, again, minimize slippage.
Another embodiment 72''' for the fourth transducer is illustrated
in FIGS. 11 and 11a. Again, there are a number of points of
similarity between the embodiments of FIGS. 11 and 11a and the
previously described embodiments of FIGS. 9 and 9a and FIGS. 10 and
10a. Therefore, like reference numerals will again refer to like
elements. In this embodiment, a sensor 134 has a shaft 136 which
serves as the axle of a friction wheel 138 which, in turn, engages
a circumferential surface of sleeve 115. Therefore, a rotation of
the shaft 110 will cause a rotation of the sleeve 115, which will
cause a rotation of the wheel 138 and the shaft 136 to create an
electrical signal on cable 30.
With reference to all of the figures, and with particular reference
to FIGS. 1 and 2, the shaft 28 of a laparoscopic tool 18 is
inserted into aperture 46 along axis A.sub.0, causing the shaft 28
to frictionally engage the translation interface (wheel) 50. In
this instance, the translational interface 50 is a friction wheel
made out of a rubber-like material. The shaft 28 is also in
engagement with the rotation interface 52 which, in the embodiment
of FIG. 2, is also a friction wheel made out of a rubber-like
material. Rotation of the shaft 28 around the axis A.sub.0 as
illustrated by the arrow r will cause a rotation of the friction
wheel 50 and therefore the shaft 82 of the sensor 72. A translation
of the shaft 28 along axis A.sub.0 will cause a rotation of the
friction wheel 50 which rotates the shaft 76 of the transducer 70.
A movement up or down of the laparoscopic tool 18 will cause a
rotation of the shaft (pivot) 48a of transducer 68, and a
side-to-side pivoting of the laparoscopic tool 18 will cause a
rotational around axis A.sub.1 which is detected by transducer
66.
To this point, the majority of the discussion has been under the
assumption that the transducers are input transducers, i.e. the
human/computer interface device is used an input device to the
computer 16. However, it is also been mentioned that the interface
device 12 can serve as an output device for the computer 16. When
used as an output device, output transducers ("actuators") are used
to respond to electrical signals developed by the computer 16 to
impart a force upon the shaft 28 of the laparoscopic tool 18. This
can provide useful movement and force (haptic) feedback to the
doctor/trainee or other user. For example, if the laparoscopic tool
encounters dense mass of tissue or a bone in the "virtual" patient,
a force can be generated by transducer 70 making it harder for the
doctor/trainee to push the shaft 28 further into the gimbal
apparatus 25. Likewise, twisting motions can be imparted on the
shaft 28 when the shaft encounters an obstacle within the virtual
patient.
It should be noted that force applied to the shaft may not result
in any movement of the shaft. This is because the shaft may be
inhibited from movement by the hand of the operator who is grasping
a handle or grip portion of the shaft. However, the force applied
to the shaft may be sensed by the operator as haptic feedback.
With reference to FIG. 2, a method for mechanically interfacing an
elongated mechanical object with an electrical system in accordance
with the present invention includes first step of defining an
origin in 3-dimensional space. This corresponds to the origin O at
the intersection of axis A.sub.1 and A.sub.2. A second step is to
physically constrain an elongated object in the 3-dimensional space
such that a portion of the object always intersects the origin O
and such that a portion of the object extending from the origin O
defines a radius in a spherical coordinate system. The elongated
object (such as shaft 28 of laparoscopic tool 18) is physically
constrained in a 3-dimensional space by the aperture 46 of the
object receiving portion 44. The portion of the shaft 28 extending
from origin O defines the radius. A third step includes transducing
a first electrical signal related to a first angular coordinate of
the radius with a first transducer. This corresponds to the
operation of transducer 66 which transduces a first electrical
signal related to a first angular coordinate of the radius. A
fourth step is transducing a second electrical signal related to a
second angular coordinate of the radius. This corresponds to the
operation of transducer 68 which transduces a second electrical
signal. A fifth step is to transduce a third electrical signal
related to the length of the radius, which corresponds to the
operation of transducer 70. A sixth and final step is to
electrically couple the transducers to an electrical system which,
in this instance, is preferably a computer 16. An additional,
optional step transduces a fourth electrical signal related to a
rotation of the object around an object axis which intersects the
origin O. This step corresponds to the operation of transducer 72.
The transducers can be input transducers, output transducers, or
bi-directional transducers.
It will be noted that the electrical system most frequently
described in the present invention is a digital processing system
or a computer. However, other digital systems, analog systems, and
simple electric or electromechanical system can also be utilized
with the apparatus and method of the present invention.
It will also be noted that while specific examples of "elongated
objects" and "shafts" have been given, that these examples are not
meant to be limiting. In general, equivalents of "elongated
objects", "elongated cylindrical objects", "shafts", etc. include
any object which can be grasped by a human operator to provide an
interface between the operator and a computer system. By "grasp",
it is meant that operators may releasably engage a grip portion of
the object in some fashion, such as by hand, with their fingertips,
or even orally in the case of handicapped persons. The "grip" can
be a functional grip or handle attached to an elongated portion of
the object, or can be a portion of the object itself, such as a
portion of the length of a shaft that can be gripped and/or
manipulated by the operator.
It should also be noted that flexible shafts, such as wires or
catheters, do not always require three or four degrees of freedom.
For example, if a human/computer interface for a catheter insertion
virtual reality system is desired, only a translation interface
(e.g. translation interface 50' of FIG. 2a) and rotation interface
(such as rotation interface 52' of FIG. 9c) may be required. This
is because a catheter can be moved in and out of a virtual patient
(as sensed by translation interface 50') and can be twisted or
rotated (as sensed by rotation interface 50'), but cannot be, in
any practical manner, moved up or down or from side-to-side due to
the flexibility of the catheter. In such applications, therefore,
it is desirable to have a human/computer interface with only two
degrees of freedom.
While this invention has been described in terms of several
preferred embodiments, it is contemplated that alternatives,
modifications, permutations and equivalents thereof will become
apparent to those skilled in the art upon a reading of the
specification and study of the drawings. It is therefore intended
that the following appended claims include all such alternatives,
modifications, permutations and equivalents as fall within the true
spirit and scope of the present invention.
* * * * *
References